Abstract:

An apparatus includes a hollow heater. The hollow heater has a hollow
supporter, a heating element and at least two electrodes. The at least
two electrodes are separately and electrically connected to the heating
element. The hollow supporter defines a hollow space, the hollow
supporter has an inner surface and an outer surface. The heating element
disposed on one of the surfaces of the hollow supporter. The heating
element includes a carbon nanotube structure. The carbon nanotube
structure includes a plurality of carbon nanotubes combined by wan der
Waals attractive force.

Claims:

1. An apparatus comprising a hollow heater, the hollow heater comprising:a
hollow supporter, the hollow supporter defines a hollow space, the hollow
supporter has an inner surface and an outer surface;a heating element,
the heating element is located adjacent to the inner surface or to the
outer surface and comprises at least one carbon nanotube structure, the
carbon nanotube structure comprises a plurality of carbon nanotubes
combined by wan der Waals attractive force; andat least two electrodes
electrically connected to the heating element.

2. The apparatus of claim 1, wherein the carbon nanotube structure is a
substantially pure structure of carbon nanotubes.

4. The apparatus of claim 1, wherein the carbon nanotubes are orderly
arranged in the carbon nanotube structure.

5. The apparatus of claim 1, wherein the heat capacity per unit area of
the carbon nanotube structure is less than 2.times.10.sup.-4 J/m2K.

6. The apparatus of claim 1, wherein the carbon nanotube structure
comprises a carbon nanotube film structure, a linear carbon nanotube
structure, or a combination thereof.

7. The apparatus of claim 6, wherein the carbon nanotube film structure
comprises at least one carbon nanotube film.

8. The apparatus of claim 6, wherein the carbon nanotube film structure
comprises two or more carbon nanotube films stacked or arranged
side-by-side.

9. The apparatus of claim 7, wherein a thickness of the carbon nanotube
film structure is in a range from about 0.5 nm to about 1 mm.

10. The apparatus of claim 6, wherein the heating element comprises two or
more linear carbon nanotube structures, the linear carbon nanotube
structures are parallel to each other, cross with each other, woven
together or twisted with each other.

11. The apparatus of claim 6, wherein a diameter of the at least one
linear carbon nanotube structure is in a range from about 0.5 nm to about
1 mm.

12. The apparatus of claim 6, wherein the at least one linear carbon
nanotube structure is a carbon nanotube wire or a carbon nanotube cable,
the carbon nanotube cable comprises two or more carbon nanotube wires.

13. The apparatus of claim 12, wherein a diameter of the carbon nanotube
wire is in a range from about 0.5 nm to about 100 μm.

14. The apparatus of claim 1, further comprising a heat-reflecting layer
configured to reflect heat emitted from the heating element.

15. The apparatus of claim 14, wherein the heating element is disposed on
the inner surface the hollow supporter, the heat-reflecting layer is
disposed on the outer surface of the hollow supporter.

16. The apparatus of claim 14, wherein the heating element is disposed on
the outer surface the hollow supporter, the heating element disposed
between the heat-reflecting layer and the hollow supporter.

17. The apparatus of claim 1, further comprising a protecting layer
configured to protect the heating element.

18. A hollow heater comprising:a hollow supporter, the hollow supporter
having an inner surface and an outer surface;a heating-reflective layer,
the heating-reflective layer disposed on the inner surface of the hollow
supporter;a carbon nanotube structure disposed on an inner surface of the
heating-reflective layer; andat least two electrodes electrically
connected to the carbon nanotube structure.

19. The hollow heater of claim 18, wherein the carbon nanotubes in the
carbon nanotube structure are orderly arranged.

20. The hollow heater of claim 18, wherein the carbon nanotubes in the
carbon nanotube structure are substantially parallel with each other.

Description:

[0004]Heaters are configured for generating heat. According to the
structures, the heaters can be divided into three types: linear heater,
planar heater and hollow heater.

[0005]The linear heater has a linear structure, and is a one-dimensional
structure. An object to be heated can be wrapped by linear heater when
the linear heater is used to heat the object. The linear heater has an
advantage of being very small in size and can be used in appropriate
applications.

[0006]The planar heater has a planar two-dimensional structure. An object
to be heated is placed near the planar structure and heated. The planar
heater provides a wide planar heating surface and an even heating to an
object. The planar heater has been widely used in various applications
such as infrared therapeutic instruments, electric heaters, etc.

[0007]The hollow heater defines a hollow space therein, and is
three-dimensional structure. An object to be heated can be placed in the
hollow space in a hollow heater. The hollow heater can apply heat in all
directions about an object and will have a high heating efficiency.
Hollow heaters have been widely used in various applications.

[0008]A typical heater includes a heating element and at least two
electrodes. The heating element is located on the two electrodes. The
heating element generates heat when a voltage is applied to it. The
heating element is often made of metal such as tungsten. Metals, which
have good conductivity, can generate a lot of heat even when a low
voltage is applied. However, metals may be easily oxidized, thus the
heater element has short life. Furthermore, since metals have a relative
high density, metal heating elements are heavy, which limits applications
of such a heater. Additionally, metal heating elements are difficult to
bend to desired shapes without breaking.

[0009]What is needed, therefore, is a heater based on carbon nanotubes
that can overcome the above-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]Many aspects of the present heater can better be understood with
reference to the following drawings. The components in the drawings are
not necessarily to scale, the emphasis instead being placed upon clearly
illustrating the principles of the present heater.

[0011]FIG. 1 is an isotropic view of a planar heater having a carbon
nanotube structure.

[0012]FIG. 2 is a schematic, cross-sectional view, along a line II-II of
FIG. 1.

[0019]FIG. 9 is an isotropic view of a hollow heater having a carbon
nanotube structure.

[0020]FIG. 10 is a schematic, cross-sectional view, along a line X-X of
FIG. 9.

[0021]FIG. 11 is an isotropic view of a hollow heater, wherein the heating
element is a linear carbon nanotube structure.

[0022]FIG. 12 is an isotropic view of a hollow heater, wherein the heating
element includes a plurality of parallel linear carbon nanotube
structures.

[0023]FIG. 13 is an isotropic view of a hollow heater, wherein the heating
element includes a plurality of woven linear carbon nanotube structures.

[0024]FIG. 14 is a flow chart of a method for fabricating the hollow
heater.

[0025]FIG. 15 is a schematic, cross-sectional view of a linear heater
according to an embodiment.

[0026]FIG. 16 is a schematic, cross-sectional view, along a line XVI-XVI
of FIG. 15.

[0027]FIG. 17 is a flow chart of a method for fabricating the linear
heater.

[0028]Corresponding reference characters indicate corresponding parts
throughout the several views. The exemplifications set out herein
illustrate at least one exemplary embodiment of the present heater, in at
least one form, and such exemplifications are not to be construed as
limiting the scope of the invention in any manner.

DETAILED DESCRIPTION

[0029]Reference will now be made to the drawings, in detail, to describe
embodiments of the heater.

[0030]Referring to FIGS. 1 and 2, the planar heater 10 according to an
embodiment is shown. The planar heater 10 includes a planar supporter 18,
a heat-reflecting layer 17, a heating element 16, a first electrode 12, a
second electrode 14, and a protecting layer 15. The heat-reflecting layer
17 is disposed on a surface of the planar supporter 18. The heating
element 16 is disposed on a surface of the heat-reflecting layer 17. The
first electrode 12 and the second electrode 14 are electrically connected
to the heating element 16. In one embodiment, the first electrode 12 and
the second electrode 14 are located on the heating element 16.

[0031]The planar supporter 18 is configured for supporting the heating
element 16 and the heat-reflecting layer 17. The planar supporter 18 is
made of flexible materials or rigid materials. The flexible materials may
be plastics, resins or fibers. The rigid materials may be ceramics,
glasses, or quartzes. When flexible materials are used, the planar heater
10 can be shaped into a desired form. The shape and size of the planar
supporter 18 can be determined according to practical needs. For example,
the planar supporter 18 may be square, round or triangular. When the
material of the planar supporter 18 is rigid, the heater 10 can maintain
a fixed shape. In one embodiment, the planar supporter 18 is a square
ceramic sheet about 1 mm thick. A planar supporter 18 is only used when
desired. The heating element 16 can be free standing structure.

[0032]The heat-reflecting layer 17 is configured for reflecting the heat
emitted by the heating element 16, and control the direction of heat from
the heating element 16 for single-side heating. The heat-reflecting layer
17 may be made of insulative materials. The material of the
heat-reflecting layer 17 can be selected from a group consisting of metal
oxides, metal salts, and ceramics. In one embodiment, the heat-reflecting
layer 17 is an aluminum oxide (Al2O3) film. A thickness of the
heat-reflecting layer 17 can be in a range from about 100 μm to about
0.5 mm. In one embodiment, the thickness of the heat-reflecting layer 17
is about 0.1 mm. The heat-reflecting layer 17 can be sandwiched between
the heating element 16 and the planar supporter 18. Alternatively, the
heat-reflecting layer 17 can be omitted, and the heating element 16 can
be located directly on the planar supporter 18 if used. In other
embodiments, the heating element can be free standing without being
attached to either a planar supporter 18 or a heat-reflecting layer 17.
When there is no heat-reflecting layer, the planar heater 10 can be used
for double-side heating.

[0033]The heating element 16 includes a carbon nanotube structure. The
carbon nanotube structure includes a plurality of carbon nanotubes
uniformly distributed therein, and the carbon nanotubes therein can be
combined by van der Waals attractive force therebetween. The carbon
nanotube structure can be a substantially pure structure of the carbon
nanotubes, with few impurities. The carbon nanotubes can be used to form
many different structures and provide a large specific surface area. The
heat capacity per unit area of the carbon nanotube structure can be less
than 2×10-4 J/m2K. Typically, the heat capacity per unit
area of the carbon nanotube structure is less than 1.7×10-6
J/m2K. As the heat capacity of the carbon nanotube structure is very
low, and the temperature of the heating element 16 can rise and fall
quickly, which makes the heating element 16 have a high heating
efficiency and accuracy. As the carbon nanotube structure can be
substantially pure, the carbon nanotubes are not easily oxidized and the
life of the heating element 16 will be relatively long. Further, the
carbon nanotubes have a low density, about 1.35 g/cm3, so the
heating element 16 is light. As the heat capacity of the carbon nanotube
structure is very low, the heating element 16 has a high response heating
speed. As the carbon nanotube has large specific surface area, the carbon
nanotube structure with a plurality of carbon nanotubes has large
specific surface area. When the specific surface of the carbon nanotube
structure is large enough, the carbon nanotube structure is adhesive and
can be directly applied to a surface.

[0034]The carbon nanotubes in the carbon nanotube structure can be
arranged orderly or disorderly. The term `disordered carbon nanotube
structure` refers to a structure where the carbon nanotubes are arranged
along many different directions, and the aligning directions of the
carbon nanotubes are random. The number of the carbon nanotubes arranged
along each different direction can be almost the same (e.g. uniformly
disordered). The disordered carbon nanotube structure can be isotropic.
The carbon nanotubes in the disordered carbon nanotube structure can be
entangled with each other.

[0035]The carbon nanotube structure including ordered carbon nanotubes is
an ordered carbon nanotube structure. The term `ordered carbon nanotube
structure` refers to a structure where the carbon nanotubes are arranged
in a consistently systematic manner, e.g., the carbon nanotubes are
arranged approximately along a same direction and/or have two or more
sections within each of which the carbon nanotubes are arranged
approximately along a same direction (different sections can have
different directions). The carbon nanotubes in the carbon nanotube
structure can be selected from a group consisting of single-walled,
double-walled, and/or multi-walled carbon nanotubes.

[0036]The carbon nanotube structure can be a carbon nanotube film
structure with a thickness ranging from about 0.5 nanometers to about 1
millimeter. The carbon nanotube film structure can include at least one
carbon nanotube film. The carbon nanotube structure can also be a linear
carbon nanotube structure with a diameter ranging from about 0.5
nanometers to about 1 millimeter. The carbon nanotube structure can also
be a combination of the carbon nanotube film structure and the linear
carbon nanotube structure. It is understood that any carbon nanotube
structure described can be used with all embodiments. It is also
understood that any carbon nanotube structure may or may not employ the
use of a support structure.

[0037]In one embodiment, the carbon nanotube film structure includes at
least one drawn carbon nanotube film. A film can be drawn from a carbon
nanotube array, to form a drawn carbon nanotube film. Examples of drawn
carbon nanotube film are taught by U.S. Pat. No. 7,045,108 to Jiang et
al., and WO 2007015710 to Zhang et al. The drawn carbon nanotube film
includes a plurality of successive and oriented carbon nanotubes joined
end-to-end by van der Waals attractive force therebetween. The drawn
carbon nanotube film is a free-standing film. Referring to FIGS. 3 to 4,
each drawn carbon nanotube film includes a plurality of successively
oriented carbon nanotube segments 143 joined end-to-end by van der Waals
attractive force therebetween. Each carbon nanotube segment 143 includes
a plurality of carbon nanotubes 145 parallel to each other, and combined
by van der Waals attractive force therebetween. As can be seen in FIG. 3,
some variations can occur in the drawn carbon nanotube film. The carbon
nanotubes 145 in the drawn carbon nanotube film are oriented along a
preferred orientation. The carbon nanotube film can be treated with an
organic solvent to increase the mechanical strength and toughness of the
carbon nanotube film and reduce the coefficient of friction of the carbon
nanotube film. A thickness of the carbon nanotube film can range from
about 0.5 nanometers to about 100 micrometers.

[0038]The carbon nanotube film structure of the heating element 16 can
include at least two stacked carbon nanotube films. In other embodiments,
the carbon nanotube structure can include two or more coplanar carbon
nanotube films, and can include layers of coplanar carbon nanotube films.
Additionally, when the carbon nanotubes in the carbon nanotube film are
aligned along one preferred orientation (e.g., the drawn carbon nanotube
film), an angle can exist between the orientation of carbon nanotubes in
adjacent films, whether stacked or adjacent. Adjacent carbon nanotube
films can be combined by only the van der Waals attractive force
therebetween. The number of the layers of the carbon nanotube films is
not limited as long as the carbon nanotube structure. However the thicker
the carbon nanotube structure, the specific surface area will decrease.
An angle between the aligned directions of the carbon nanotubes in two
adjacent carbon nanotube films can range from about 0° to about
90°. When the angle between the aligned directions of the carbon
nanotubes in adjacent carbon nanotube films is larger than 0 degrees, a
microporous structure is defined by the carbon nanotubes in the heating
element 16. The carbon nanotube structure in an embodiment employing
these films will have a plurality of micropores. Stacking the carbon
nanotube films will also add to the structural integrity of the carbon
nanotube structure. In some embodiments, the carbon nanotube structure
has a free standing structure and does not require the use of the planar
supporter 18.

[0039]In another embodiment, the carbon nanotube film structure includes a
flocculated carbon nanotube film. Referring to FIG. 5, the flocculated
carbon nanotube film can include a plurality of long, curved, disordered
carbon nanotubes entangled with each other. Further, the flocculated
carbon nanotube film can be isotropic. The carbon nanotubes can be
substantially uniformly dispersed in the carbon nanotube film. Adjacent
carbon nanotubes are acted upon by van der Waals attractive force to form
an entangled structure with micropores defined therein. It is understood
that the flocculated carbon nanotube film is very porous. Sizes of the
micropores can be less than 10 micrometers. The porous nature of the
flocculated carbon nanotube film will increase specific surface area of
the carbon nanotube structure. Further, due to the carbon nanotubes in
the carbon nanotube structure being entangled with each other, the carbon
nanotube structure employing the flocculated carbon nanotube film has
excellent durability, and can be fashioned into desired shapes with a low
risk to the integrity of the carbon nanotube structure. The flocculated
carbon nanotube film, in some embodiments, will not require the use of
the planar supporter 18 due to the carbon nanotubes being entangled and
adhered together by van der Waals attractive force therebetween. The
thickness of the flocculated carbon nanotube film can range from about
0.5 nanometers to about 1 millimeter.

[0040]In another embodiment, the carbon nanotube film structure can
include at least a pressed carbon nanotube film. Referring to FIG. 6, the
pressed carbon nanotube film can be a free-standing carbon nanotube film.
The carbon nanotubes in the pressed carbon nanotube film are arranged
along a same direction or arranged along different directions. The carbon
nanotubes in the pressed carbon nanotube film can rest upon each other.
Adjacent carbon nanotubes are attracted to each other and combined by van
der Waals attractive force. An angle between a primary alignment
direction of the carbon nanotubes and a surface of the pressed carbon
nanotube film is 0 degrees to approximately 15 degrees. The greater the
pressure applied, the smaller the angle formed. When the carbon nanotubes
in the pressed carbon nanotube film are arranged along different
directions, the carbon nanotube structure can be isotropic. The thickness
of the pressed carbon nanotube film ranges from about 0.5 nm to about 1
mm. Examples of pressed carbon nanotube film are taught by US application
20080299031A1 to Liu et al.

[0042]The carbon nanotube wire can be untwisted or twisted. Treating the
drawn carbon nanotube film with a volatile organic solvent can form the
untwisted carbon nanotube wire. Specifically, the organic solvent is
applied to soak the entire surface of the drawn carbon nanotube film.
During the soaking, adjacent parallel carbon nanotubes in the drawn
carbon nanotube film will bundle together, due to the surface tension of
the organic solvent as it volatilizes, and thus, the drawn carbon
nanotube film will be shrunk into untwisted carbon nanotube wire.
Referring to FIG. 7, the untwisted carbon nanotube wire includes a
plurality of carbon nanotubes substantially oriented along a same
direction (i.e., a direction along the length of the untwisted carbon
nanotube wire). The carbon nanotubes are parallel to the axis of the
untwisted carbon nanotube wire. More specifically, the untwisted carbon
nanotube wire includes a plurality of successive carbon nanotube segments
joined end to end by van der Waals attractive force therebetween. Each
carbon nanotube segment includes a plurality of carbon nanotubes
substantially parallel to each other, and combined by van der Waals
attractive force therebetween. The carbon nanotube segments can vary in
width, thickness, uniformity and shape. Length of the untwisted carbon
nanotube wire can be arbitrarily set as desired. A diameter of the
untwisted carbon nanotube wire ranges from about 0.5 nm to about 100
μm.

[0043]The twisted carbon nanotube wire can be formed by twisting a drawn
carbon nanotube film using a mechanical force to turn the two ends of the
drawn carbon nanotube film in opposite directions. Referring to FIG. 8,
the twisted carbon nanotube wire includes a plurality of carbon nanotubes
helically oriented around an axial direction of the twisted carbon
nanotube wire. More specifically, the twisted carbon nanotube wire
includes a plurality of successive carbon nanotube segments joined end to
end by van der Waals attractive force therebetween. Each carbon nanotube
segment includes a plurality of carbon nanotubes parallel to each other,
and combined by van der Waals attractive force therebetween. Length of
the carbon nanotube wire can be set as desired. A diameter of the twisted
carbon nanotube wire can be from about 0.5 nanometers to about 100
micrometers. Further, the twisted carbon nanotube wire can be treated
with a volatile organic solvent after being twisted. After being soaked
by the organic solvent, the adjacent paralleled carbon nanotubes in the
twisted carbon nanotube wire will bundle together, due to the surface
tension of the organic solvent when the organic solvent volatilizing. The
specific surface area of the twisted carbon nanotube wire will decrease,
while the density and strength of the twisted carbon nanotube wire will
be increased.

[0044]The carbon nanotube cable includes two or more carbon nanotube
wires. The carbon nanotube wires in the carbon nanotube cable can be,
twisted or untwisted. In an untwisted carbon nanotube cable, the carbon
nanotube wires are parallel to each other. In a twisted carbon nanotube
cable, the carbon nanotube wires are twisted with each other.

[0045]The heating element 16 can include a plurality of linear carbon
nanotube structures. The plurality of linear carbon nanotube structures
can be paralleled with each other, cross with each other, weaved
together, or twisted with each other. The resulting structure can be a
planar structure if so desired.

[0046]The first electrode 12 and the second electrode 14 can be disposed
on a same surface or opposite surfaces of the heating element 16.
Furthermore, it is imperative that the first electrode 12 be separated
from the second electrode 14 to prevent short circuiting of the
electrodes. The first electrode 12 and the second electrode 14 can be
directly electrically attached to the heating element 16 by, for example,
a conductive adhesive (not shown), such as silver adhesive. Because, some
of the carbon nanotube structures have large specific surface area and
are adhesive in nature, in some embodiments, the first electrode 12 and
the second electrode 14 can be adhered directly to heating element 16. It
should be noted that any other bonding ways may be adopted as long as the
first electrode 12 and the second electrode 14 are electrically connected
to the heating element 16. The shape of the first electrode 12 or the
second electrode 14 is not limited and can be lamellar, rod, wire, and
block among other shapes. In the embodiment shown in FIG. 1, the first
electrode 12 and the second electrode 14 are both lamellar and parallel
to each other. The material of the first electrode 12 and the second
electrode 14 can be selected from metals, conductive resins, or any other
suitable materials. In some embodiments, the carbon nanotubes in the
heating element 16 are aligned along a direction perpendicular to the
first electrode 12 and the second electrode 14. In other embodiments, at
least one of the first electrode 12 and the second electrode 14 includes
at least a carbon nanotube film or at least a linear carbon nanotube
structure. In one embodiment, each of the first electrode 12 and the
second electrode 14 includes a linear carbon nanotube structure. The
linear carbon nanotube structures are separately disposed on the two ends
of the heating element 16.

[0047]The protecting layer 15 is disposed on a surface of the heating
element 16. In one embodiment, the protecting layer 15 fully covers a
surface of the heating element 16. The protecting layer 15 and the
heat-reflecting layer 17 are located at two opposite flanks of the
heating element 16. The material of protecting layer 15 can be electric
or insulative. The electric material can be metal or alloy. The
insulative material can be resin, plastic or rubber. A thickness of the
protecting layer 15 can range from about 0.5 μm to about 2 mm. When
the material of the protecting layer 15 is insulative, the protecting
layer 15 can electrically and/or thermally insulate the planar heater 10
from the external environment. The protecting layer 15 can also protect
the heating element 16 from outside contaminants. The protecting layer 15
is an optional structure and can be omitted.

[0048]In use, when a voltage is applied to the first electrode 12 and the
second electrode 14 of the planar heater 10, and the carbon nanotube
structure of the heating element 16 radiates heat at a certain
wavelength. The object to be heated can be directly attached on the
planar heater 10 or separated from the planar heater 10. By controlling
the specific surface area of the heating element 16, varying the voltage
and the thickness of the heating element 16, the heating element 16 emits
heat at different wavelengths. If the voltage is determined at a certain
value, the wavelength of the electromagnetic waves emitted from the
heating element 16 is inversely proportional to the thickness of the
heating element 16. That is to say, the greater the thickness of heating
element 16 is, the shorter the wavelength of the electromagnetic waves
is. Further, if the thickness of the heating element 16 is determined at
a certain value, the greater the voltage applied to the electrode, the
shorter the wavelength of the electromagnetic waves. As such, the planar
heater 10, can easily be controlled for emitting a visible light and
create general thermal radiation or emit infrared radiation.

[0049]Further, due to carbon nanotubes having an ideal black body
structure, the heating element 16 has excellent electrical conductivity,
thermal stability, and high thermal radiation efficiency. The planar
heater 10 can be safely exposed, while working, to oxidizing gases in a
typical environment. The planar heater 10 can radiate an electromagnetic
wave with a long wavelength when a voltage is applied on the planar
heater 10. In one embodiment, the heating element 16 includes one hundred
layers of drawn carbon nanotubes stacked on each other, and the
orientation of the carbon nanotubes in the adjacent two carbon nanotubes
are perpendicular with each other. Each drawn carbon nanotube film has a
square shape with an area of 15 cm2. A thickness of the carbon
nanotube structure is about 10 μm. When the voltage ranges from 10
volts to 30 volts, the temperature of the planar heater 10 ranges from
50° C. to 500° C. As an ideal black body structure, the
carbon nanotube structure 16 can radiate heat when it reaches a
temperature of 200° C. to 450° C. The radiating efficiency
is relatively high. Thus, the planar heater 10 can be used in electric
heaters, infrared therapy devices, electric radiators, and other related
devices.

[0050]Further, the planar heater 10 can be disposed in a vacuum device or
a device with inert gas filled therein. When the voltage is increased in
the approximate range from 80 volts to 150 volts, the planar heater 10
emits electromagnetic waves having a relatively short wave length such as
visible light (e.g. red light, yellow light etc), general thermal
radiation, and ultraviolet radiation. The temperature of the planar
source 10 can reach 1500° C. When the voltage on the planar heater
10 is high enough, the planar heater 10 can eradiate ultraviolet to kill
bacteria.

[0051]A method for making a planar heater 10 is disclosed. The method
includes the steps of:

[0052]S1: providing a planar supporter 18;

[0053]S2: making a carbon nanotube structure;

[0054]S3: fixing the carbon nanotube structure on a surface of the planar
supporter 18; and

[0055]S4: providing a first electrode 12 and a second electrode 14
separately and electrically connected to the heating element 16.

[0056]It is to be understood that, before step S3, an additional step of
forming a heat-reflecting layer 17 attached to a surface of the planar
supporter 18 can be performed. And the carbon nanotube structure is
disposed on the surface of heat-reflecting layer 17, e.g. the
heat-reflecting layer is located between the planar supporter 18 and the
carbon nanotube structure. The heat-reflecting layer 17 can be formed by
coating method, chemical deposition method, ion sputtering method, and so
on. In one embodiment, the heat-reflecting layer 17 is a film made of
aluminum oxide. The heat-reflecting layer 17 is coated to the heating
element 16. After step S4, an additional step of forming a protecting
layer 15 to cover the carbon nanotube structure can be carried out. The
protecting layer 15 can be form by a sputtering method or a coating
method.

[0057]In step S2, the carbon nanotube structure includes carbon nanotube
films and linear carbon nanotube structures. The carbon nanotube films
can be a drawn carbon nanotube film, a pressed carbon nanotube film or a
flocculated carbon nanotube film, or a combination thereof.

[0058]In step S2, a method of making a drawn carbon nanotube film includes
the steps of:

[0059]S21: providing an array of carbon nanotubes; and

[0060]S22: pulling out at least a drawn carbon nanotube film from the
carbon nanotube array.

[0061]In step S21, a method of forming the array of carbon nanotubes
includes:

[0062]S211: providing a substantially flat and smooth substrate;

[0063]S212: forming a catalyst layer on the substrate;

[0064]S213: annealing the substrate with the catalyst at a temperature in
the approximate range of 700° C. to 900° C. in air for
about 30 to 90 minutes;

[0065]S214: heating the substrate with the catalyst at a temperature in
the approximate range from 500° C. to 740° C. in a furnace
with a protective gas therein; and

[0066]S215: supplying a carbon source gas to the furnace for about 5 to 30
minutes and growing a super-aligned array of the carbon nanotubes from
the substrate.

[0067]In step S211, the substrate can be a P or N-type silicon wafer.
Quite suitably, a 4-inch P-type silicon wafer is used as the substrate.

[0068]In step S212, the catalyst can be made of iron (Fe), cobalt (Co),
nickel (Ni), or any combination alloy thereof.

[0069]In step S214, the protective gas can be made up of at least one of
nitrogen (N2), ammonia (NH3), and a noble gas.

[0070]In step S215, the carbon source gas can be a hydrocarbon gas, such
as ethylene (C2H4), methane (CH4), acetylene
(C2H2), ethane (C2H6), or any combination thereof.

[0071]In step S22, a drawn carbon nanotube film can be formed by the steps
of:

[0072]S221: selecting one or more carbon nanotubes having a predetermined
width from the array of carbon nanotubes; and

[0073]S222: pulling the carbon nanotubes to form nanotube segments at an
even/uniform speed to achieve a uniform carbon nanotube film.

[0074]In step S221, the carbon nanotube segment includes a plurality of
parallel carbon nanotubes. The carbon nanotube segments can be selected
by using an adhesive tape as the tool to contact the super-aligned array
of carbon nanotubes. In step S222, the pulling direction is substantially
perpendicular to the growing direction of the super-aligned array of
carbon nanotubes.

[0075]More specifically, during the pulling process, as the initial carbon
nanotube segments are drawn out, other carbon nanotube segments are also
drawn out end to end due to van der Waals attractive force between ends
of adjacent segments. This process of pulling produces a substantially
continuous and uniform carbon nanotube film having a predetermined width
can be formed.

[0076]After the step of S22, the drawn carbon nanotube film can be treated
by applying organic solvent to the drawn carbon nanotube film to soak the
entire surface of the carbon nanotube film. The organic solvent is
volatile and can be selected from the group consisting of ethanol,
methanol, acetone, dichloromethane, chloroform, any appropriate mixture
thereof. In the one embodiment, the organic solvent is ethanol. After
being soaked by the organic solvent, adjacent carbon nanotubes in the
carbon nanotube film that are able to do so, bundle together, due to the
surface tension of the organic solvent when the organic solvent is
volatilizing. In another aspect, due to the decrease of the specific
surface area via bundling, the mechanical strength and toughness of the
drawn carbon nanotube film are increased and the coefficient of friction
of the carbon nanotube films is reduced. Macroscopically, the drawn
carbon nanotube film will be an approximately uniform film.

[0077]The width of the drawn carbon nanotube film depends on a size of the
carbon nanotube array. The length of the drawn carbon nanotube film can
be set as desired. In one embodiment, when the substrate is a 4 inch type
wafer as in the present embodiment, a width of the carbon nanotube film
can be in an approximate range from 1 centimeter to 10 centimeters, a
length of the carbon nanotube film can reach to about 120 m, a thickness
of the drawn carbon nanotube film can be in an approximate range from 0.5
nanometers to 100 microns. Multiple films can be adhered together to form
a film of any desired size.

[0078]In step S2, a method of making the pressed carbon nanotube film
includes the following steps:

[0079]S21': providing a carbon nanotube array and a pressing device; and

[0080]S22': pressing the array of carbon nanotubes to form a pressed
carbon nanotube film.

[0081]In step S21', the carbon nanotube array can be made by the same
method as S11.

[0082]In the step S22', a certain pressure can be applied to the array of
carbon nanotubes by the pressing device. In the process of pressing, the
carbon nanotubes in the array of carbon nanotubes separate from the
substrate and form the carbon nanotube film under pressure. The carbon
nanotubes are substantially parallel to a surface of the carbon nanotube
film.

[0083]In one embodiment, the pressing device can be a pressure head. The
pressure head has a smooth surface. It is to be understood that, the
shape of the pressure head and the pressing direction can determine the
direction of the carbon nanotubes arranged therein. When a pressure head
(e.g a roller) is used to travel across and press the array of carbon
nanotubes along a predetermined single direction, a carbon nanotube film
having a plurality of carbon nanotubes primarily aligned along a same
direction is obtained. It can be understood that there may be some
variation in the film. Different alignments can be achieved by applying
the roller in different directions over an array. Variations on the film
can also occur when the pressure head is used to travel across and press
the array of carbon nanotubes several of times, variation will occur in
the orientation of the nanotubes. Variations in pressure can also achieve
different angles between the carbon nanotubes and the surface of the
semiconducting layer on the same film. When a planar pressure head is
used to press the array of carbon nanotubes along the direction
perpendicular to the substrate, a carbon nanotube film having a plurality
of carbon nanotubes isotropically arranged can be obtained. When a
roller-shaped pressure head is used to press the array of carbon
nanotubes along a certain direction, a carbon nanotube film having a
plurality of carbon nanotubes aligned along the certain direction is
obtained. When a roller-shaped pressure head is used to press the array
of carbon nanotubes along different directions, a carbon nanotube film
having a plurality of sections having carbon nanotubes aligned along
different directions is obtained.

[0084]In step S2, the flocculated carbon nanotube film can be made by the
following method:

[0085]S21'': providing a carbon nanotube array;

[0086]S22'': separating the array of carbon nanotubes from the substrate
to get a plurality of carbon nanotubes;

[0087]S23'': adding the plurality of carbon nanotubes to a solvent to get
a carbon nanotube floccule structure in the solvent; and

[0088]S24'': separating the carbon nanotube floccule structure from the
solvent, and shaping the separated carbon nanotube floccule structure
into a carbon nanotube film to achieve a flocculated carbon nanotube
film.

[0089]In step S21'', the carbon nanotube array can be formed by the same
method as step (a1).

[0090]In step S22'', the array of carbon nanotubes is scraped off the
substrate to obtain a plurality of carbon nanotubes. The length of the
carbon nanotubes can be above 10 microns.

[0091]In step S23'', the solvent can be selected from a group consisting
of water and volatile organic solvent. After adding the plurality of
carbon nanotubes to the solvent, a process of flocculating the carbon
nanotubes can, suitably, be executed to create the carbon nanotube
floccule structure. The process of flocculating the carbon nanotubes can
be selected from the group consisting of ultrasonic dispersion of the
carbon nanotubes and agitating the carbon nanotubes. In one embodiment
ultrasonic dispersion is used to flocculate the solvent containing the
carbon nanotubes for about 10˜30 minutes. Due to the carbon
nanotubes in the solvent having a large specific surface area and the
tangled carbon nanotubes having a large van der Waals attractive force,
the flocculated and tangled carbon nanotubes form a network structure
(i.e., floccule structure).

[0092]In step S24'', the process of separating the floccule structure from
the solvent includes the substeps of:

[0093]S24''1: filtering out the solvent to obtain the carbon nanotube
floccule structure; and

[0095]In step S24''1, the carbon nanotube floccule structure can be
disposed in room temperature for a period of time to dry the organic
solvent therein. The time of drying can be selected according to
practical needs. The carbon nanotubes in the carbon nanotube floccule
structure are tangled together.

[0096]In step S24''2, the process of shaping includes the substeps of:

[0097]S24''21: putting the separated carbon nanotube floccule structure
into a container (not shown), and spreading the carbon nanotube floccule
structure to form a predetermined structure;

[0098]S24''22: pressing the spread carbon nanotube floccule structure with
a certain pressure to yield a desirable shape; and

[0099]S24''23: removing the residual solvent contained in the spread
floccule structure to form the flocculated carbon nanotube film.

[0100]Through the flocculating, the carbon nanotubes are tangled together
by van der Walls attractive force to form a network structure/floccule
structure. Thus, the flocculated carbon nanotube film has good tensile
strength. The flocculated carbon nanotube film includes a plurality of
micropores formed by the disordered carbon nanotubes. A diameter of the
micropores can be less than about 100 micron. As such, a specific area of
the flocculated carbon nanotube film is extremely large. Additionally,
the pressed carbon nanotube film is essentially free of a binder and
includes a large amount of micropores. The method for making the
flocculated carbon nanotube film is simple and can be used in mass
production.

[0101]In step S2, a linear carbon nanotube structure includes carbon
nanotube wires and/or carbon nanotube cables. The carbon nanotube wire
can be made by the following steps:

[0102]S21''': making a drawn carbon nanotube film; and

[0103]S22''': treating the drawn carbon nanotube film to form a carbon
nanotube wire.

[0104]In step S21''', the method for making the drawn carbon nanotube film
is the same the step S21.

[0105]In step S22''', the drawn carbon nanotube film is treated with a
organic solvent to form an untwisted carbon nanotube wire or is twisted
by a mechanical force (e.g., a conventional spinning process) to form a
twist carbon nanotube wire. The organic solvent is volatilizable and can
be selected from the group consisting of ethanol, methanol, acetone,
dichloroethane, and chloroform. After soaking in the organic solvent, the
carbon nanotube segments in the carbon nanotube film can at least
partially bundle into the untwisted carbon nanotube wire due to the
surface tension of the organic solvent.

[0106]It is to be understood that a narrow carbon nanotube film can serve
as a wire. In this situation, through microscopically view, the carbon
nanotube structure is a flat film, and through macroscopically view, the
narrow carbon nanotube film would look like a long wire.

[0107]In step S2, the carbon nanotube cable can be made by bundling two or
more carbon nanotube wires together. The carbon nanotube cable can be
twisted or untwisted. In the untwisted carbon nanotube cable, the carbon
nanotube wires are parallel to each other, and the carbon nanotubes can
be kept together by an adhesive (not shown). In the twisted carbon
nanotube cable, the carbon nanotube wires twisted with each other, and
can be adhered together by an adhesive or a mechanical force.

[0108]In step S2, the drawn carbon nanotube film, the pressed carbon
nanotube film, the flocculated carbon nanotube film, or the linear carbon
nanotube structure can be overlapped, stacked with each other, and/or
disposed side by side to make a carbon nanotube structure. It is also
understood that this carbon nanotube structure can be employed by all
embodiments.

[0109]In step S3, the carbon nanotube structure can be fixed on the
surface of the planar supporter 18 with an adhesive or by a mechanical
force.

[0110]In step S4, the first electrode 12 and the second electrode 14 are
made of conductive materials, and formed on the surface of the heating
element 16 by sputtering method or coating method. The first electrode 12
and the second electrode 14 can also be attached on the heating element
16 directly with a conductive adhesive or by a mechanical force. Further,
silver paste can be applied on the surface of the heating element 16
directly to form the first electrode 12 and the second electrode 14.

[0111]Referring to FIGS. 9 and 10, a hollow heater 20 is shown. The hollow
heater 20 includes a hollow supporter 28, a heating element 26, a first
electrode 22, a second electrode 24, and a heat-reflecting layer 27. The
heating element 26 is disposed on an outer circumferential surface of the
hollow supporter 28. The heat-reflecting layer 27 is disposed on an outer
circumferential surface of the heating element 26. The hollow supporter
28 and the heat-reflecting layer 27 are located at two opposite
circumferential surfaces of the heating element 26. The first electrode
22 and the second electrode 24 are electrically connected to the heating
element 26 and spaced from each other. In one embodiment, the first
electrode 22 and the second electrode 24 are located on opposite ends of
the heat-reflecting layer 27.

[0112]The hollow supporter 28 is configured for supporting the heating
element 22 and the heat-reflecting layer 27. The hollow supporter 28
defines a hollow space 282. The shape and size of the hollow supporter 28
can be determined according to practical demands. For example, the hollow
supporter 28 can be shaped as a hollow cylinder, a hollow ball, or a
hollow cube, for example. Other characters of the hollow supporter 28 are
the same as the planar supporter 18 disclosed herein. In one embodiment,
the hollow supporter 28 is a hollow cylinder.

[0113]The heating element 26 can be attached on the inner surface or
wrapped on the outer surface of the hollow supporter 28. In the
embodiment shown in FIGS. 9 and 10, the heating element 26 is disposed on
the outer circumferential surface of the hollow supporter 28. The heating
element 26 can be fixed on the hollow supporter 28 with an adhesive (not
shown) or by a mechanical force. The same as the heating element 16
discussed above, the heating element 26 includes a carbon nanotube
structure. The characters of the carbon nanotube structure are the same
as the carbon nanotube structure disclosed in the above. All embodiments
of the carbon nanotube structure discussed above can be incorporated into
the hallow heater 20. Same as disclosed herein, the carbon nanotube
structure can be a carbon nanotube film structure, a linear carbon
nanotube structure or a combination thereof. Referring to FIG. 11, the
heating element 26 includes one linear carbon nanotube structure 160, the
linear carbon nanotube structure 160 can twist about the hollow supporter
28 like a helix. In another example, referring to FIG. 12, when the
heating element 26 includes two or more linear carbon nanotube structures
160, the linear carbon nanotube structures 160 can be disposed on the
surface of the hollow supporter 28 and parallel to each other. The linear
carbon nanotube structure can be disposed side by side or separately. In
other examples, referring to FIG. 13, when the heating element 26
includes a plurality of linear carbon nanotube structures 160, the linear
carbon nanotube structures 160 can be knitted to form a net disposed on
the surface of the hollow supporter 28. It is understood that these
linear carbon nanotube structures 160 can be applied to the inside of the
supporter 28. It is understood that in some embodiments, some of the
carbon nanotube structures have large specific surface area and adhesive
nature, such that the heating element 26 can be adhered directly to
surface of the hollow supporter 28.

[0114]The first electrode 22 and the second electrode 24 can be disposed
on a same surface or opposite surfaces of the heating element 26.
Furthermore, it is imperative that the first electrode 22 be separated
from the second electrode 24 to prevent short circuiting of the
electrodes. The first electrode 22 and the second electrode 24 can be the
same as the first electrode 12 and the second electrode 14 discussed
above. All embodiments of the electrodes discussed herein can be
incorporated into the hollow heater 20. In the embodiment shown in FIG.
9, the first electrode 22 and the second electrode 24 are both wire ring
surrounded the heating element 26 and parallel to each other. And each of
the first electrode 22 and the second electrode 24 includes a linear
carbon nanotube structure. The linear carbon nanotube structures disposed
on the two ends of the heating element 26, and wrap the heating element
26 to form two wire rings.

[0115]The heat-reflecting layer 27 can be located on the inner surface of
the hollow supporter 28, and the heating element 26 is disposed on the
inner surface of the heat-reflecting layer 27. In a second example, the
heat-reflecting layer 27 can be located on the outer surface of the
hollow supporter 28, and the heating element 26 is disposed on the inner
surface of the hollow supporter 28. Alternatively, the heat-reflecting
layer 27 can be omitted. Without the heat-reflecting layer 27, the
heating element 26 can be located directly on the hollow supporter 28.
The other properties of the heat-reflecting layer 27 are the same as the
heat-reflecting layer 17 discussed above.

[0116]When one of the inner circumferential and the outer circumferential
surfaces of the heating element 26 is exposed to air, the hollow heater
20 can further include a protecting layer (not shown) attached to the
exposed surface of the heating element 26. The protecting layer can
protect the hollow heater 20 from the environment. The protecting layer
can also protect the heating element 26 from impurities. In one
embodiment, the heating element 26 is disposed between the hollow
supporter 28 and the heat-reflecting layer 27, therefore a protecting
layer would not necessarily be needed.

[0117]In use of the hollow heater 20, an object that will be heated can be
disposed in the hollow space 282. When a voltage is applied to the first
electrode 22 and the second electrode 24, the carbon nanotube structure
of the heating element 26 of the hollow heater 20 generates heat. As the
object is disposed in the hollow space 282, the whole body of the object
can be heated equally.

[0118]A method for making a hollow heater 20 is disclosed. The method
includes the steps of:

[0119]M1: providing a hollow supporter 28;

[0120]M2: making a carbon nanotube structure;

[0121]M3: fixing the carbon nanotube structure on a surface of the hollow
supporter 28; and

[0122]M4: providing a first electrode 22 and a second electrode 24 and
electrically connecting them to the carbon nanotube structure.

[0123]It is to be understood that, after step M3, additional step of
forming a heat-reflecting layer 27 attached to the heating element 26 is
provided. The heat-reflecting layer 27 can be formed by coating method,
chemical deposition method, ion sputtering method, and so on. In one
embodiment, the heat-reflecting layer 27 is a film made of aluminum oxide
and is coated on the heating element 26.

[0124]In step M2, the detailed process of making the carbon nanotube
structure is the same as the step S2 disclosed herein.

[0125]In step M3, the carbon nanotube structure can be fixed on an inner
or an outer surface of the hollow supporter 28 with an adhesive or by
mechanical method. In some embodiments, the carbon nanotube structure can
be directly fixed on the hollow supporter directly because of the
adhesive nature of the carbon nanotube structure. The carbon nanotube
structure can wrap the outer surface of the hollow supporter 28.

[0126]The detail process of the step M4 can be the same as the step S4 in
the first embodiment.

[0127]Referring FIGS. 15 and 16, a linear heater 30 is provided. The
linear heater 30 includes a linear supporter 38, a reflecting layer 37, a
heating element 36, a first electrode 32, a second electrode 34, and a
protecting layer 35. The reflecting layer 37 is on the surface of the
linear supporter 38; the heating element 36 wraps the surface of the
reflecting layer 37. The first electrode 32 and the second electrode 34
are separately connected to the heating element 36. In one embodiment,
the first electrode 32 and the second electrode 34 are located on the
heating element 36. The protecting layer 35 covers the heating element
36, the first electrode 32 and the second electrode 34. A diameter of the
linear heater 30 is very small compared with a length of itself. In one
embodiment, the diameter of the linear heater 30 is in a range from about
1 μm to about 1 cm. A ratio of length to diameter of the linear heater
30 can be in a range from about 50 to about 5000.

[0128]The linear supporter 38 is configured for supporting the heating
element 36 and the heat-reflecting layer 37. The linear supporter 38 has
a linear structure, and the diameter of the linear supporter 38 is small
compared with a length of the linear supporter 38. Other characters of
the linear supporter 38 can be the same as the planar supporter 18 as
disclosed herein.

[0129]The heating element 36 can be attached on the surface of the linear
supporter 38 directly. When the heat-reflecting layer 37 wraps on the
surface of the linear supporter 38, the heating element 36 can be
attached on the surface of the heat-reflecting layer 37. The same as the
heating element 16 in the first embodiment, the heating element 36
includes a carbon nanotube structure. The characters of the carbon
nanotube structure can be the same as the carbon nanotube structure
discussed above.

[0130]The first electrode 32 and the second electrode 34 can be disposed
on a same surface or opposite surfaces of the heating element 36. The
shape of the first electrode 32 or the second electrode 34 is not limited
and can be lamellar, rod, wire, and block among other shapes. In the
embodiment shown in FIGS. 15 and 16, the first electrode 32 and the
second electrode 34 are both lamellar rings. In some embodiments, the
carbon nanotubes in the heating element 36 are aligned along a direction
perpendicular to the first electrode 32 and the second electrode 34. In
other embodiments, at least one of the first electrode 32 and the second
electrode 34 includes at least one carbon nanotube film or at least a
linear carbon nanotube structure. In other embodiments, each of the first
electrode 32 and the second electrode 34 includes a linear carbon
nanotube structure. The linear carbon nanotube structures disposed on the
two ends of the heating element 36, and wrap the heating element 36 to
form two rings.

[0131]The protecting layer 35 is disposed on the outer surface of the
heating element 36. In one embodiment, the protecting layer 35 fully
covers the outer surface of the heating element 36. The heating element
36 is located between the protecting layer 35 and the heat-reflecting
layer 37.

[0132]In use of the linear heater 30, the heater 30 can be twisted about a
target like a helix, and the target will be heated from outside. The
heater 30 can also be inserted into the target to heat the target form
inside. Given the small size of the linear heater 30, it can be used in
applications with limited space or in the field of MEMS for example.

[0133]Referring FIG. 17, a method for making a linear heater 30 is
provided. The method includes the steps of:

[0134]N1: providing a linear supporter 38;

[0135]N2: making a carbon nanotube structure;

[0136]N3: fixing the carbon nanotube structure on a surface of the linear
supporter 38; and

[0137]N4: providing a first electrode 32 and a second electrode 34.

[0138]It is to be understood that, before step N3, additional steps of
forming a reflecting layer 37 on the linear supporter 38 can be further
processed. After step N4, an additional step of forming a protecting
layer 35 on the heating element 36, the first electrode 32 and the second
electrode 34 can be further processed.

[0139]In step N2, the detailed process of making the carbon nanotube
structure can be the same as the step S2 discussed above.

[0140]In step N3, the carbon nanotube structure can be fixed on the
surface of the linear supporter 38 with an adhesive or by mechanical
method. In some embodiments, the carbon nanotube structure can be
directly adhered on the linear supporter because of the adhesive nature
of the carbon nanotube structure. The carbon nanotube structure can wrap
the surface of the linear supporter 38. When the carbon nanotube
structure includes a plurality of carbon nanotubes substantially oriented
along a same direction, the oriented direction can be from one end of the
supporter 38 to another end of the supporter 38.

[0141]The detail process of the step N4 can be the same as the step S4
discussed above.

[0142]It is to be understood that the above-described embodiments are
intended to illustrate rather than limit the invention. Variations may be
made to the embodiments without departing from the spirit of the
invention as claimed. It is understood that any element of any one
embodiment is considered to be disclosed to be incorporated with any
other embodiment. The above-described embodiments illustrate the scope of
the invention but do not restrict the scope of the invention.

[0143]It is also to be understood that above description and the claims
drawn to a method may include some indication in reference to certain
steps. However, the indication used is only to be viewed for
identification purposes and not as a suggestion as to an order for the
steps.